Among fluid delivery devices, especially for medical applications, there is often a need to provide an environmental seal around a fluid pathway as it passes from one environment to another and/or where one cannula portion is joined to another. Such an environmental seal might, for example, serve to exclude water from the interior of a device, such as an infusion pump. Such an environmental seal might also serve to exclude the passage of air from one environment to another to limit the transmission of microorganisms from one environment to another, or to maintain the integrity of the fluid pathway at the junction between two cannulas forming the pathway. It is well known to create such an environmental seal by inserting a pierceable membrane in a carrier element. However, since it is often desirable to make medical devices as small as possible, there is a corresponding need to make an environmental seal as small as possible without compromising the quality and reliability of the seal. Further, since such seals may be useful in devices that are intended to have short useful lives, it is also desirable to manufacture such devices at the lowest possible cost. Unfortunately, known methods for assembling environmental seals are not well suited for miniaturization with high quality and reliability and low cost.